1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly to a so-called in-plane electric field type of liquid crystal display (LCD) device or a so-called in plane switching (IPS) type of liquid crystal display device.
2. Description of the Related Art
A so-called in-plane electric field type of liquid crystal display device is constituted such that pixel electrodes and counter electrodes which generate an electric field therebetween are formed on pixel regions at a liquid-crystal-side surface of one of the respective substrates which are arranged to face each other by way of a liquid crystal and the liquid crystal is responsive to components of the electric field substantially parallel to the substrates.
In an active matrix type of liquid crystal display device adopting such a constitution, first of all, on the liquid-crystal-side surface of the above-mentioned one substrate, respective regions which are surrounded by a plurality of gate signal lines which are arranged in parallel and a plurality of drain signal lines which cross these respective gate signal lines and are arranged in parallel are formed as pixel regions.
Here, each pixel region is provided with a thin film transistor which is operated in response to a scanning signal from the gate signal line, the pixel electrode to which a video signal is supplied from the drain signal line through the thin film transistor, and the counter electrode to which a signal which becomes the reference with respect to the video signal is supplied.
Here, the pixel electrodes and the counter electrodes are respectively formed in a strip-shaped pattern which extend in one direction and these respective electrodes are formed of two pieces or more in number and are usually arranged alternately.
Further, with respect to such a constitution, there has been also known a constitution in which the counter electrodes are formed on upper surfaces of insulation films which are formed so as to cover the drain signal lines, and the drain signal lines and the center axes of the insulation films are substantially aligned, and the insulation films have a width larger than a width of the drain signal lines, and the insulation films are formed along the drain signal lines.
Such a constitution is provided for facilitating an electric line of force from the drain signal lines to terminate at the counter electrodes arranged above the drain signal lines and for preventing the electric line of force from terminating at the pixel electrodes. When the electric line of force terminates at the pixel electrodes, this gives rise to noises.
On the other hand, the liquid crystal display device having such a constitution requires counter voltage signal lines for supplying a signal to the counter electrodes and the counter voltage signal lines are arranged to run within the pixel regions so that there has been a drawback that the counter voltage signal lines impede the enhancement of a so-called numerical aperture of the pixel region.
Further, the counter electrodes and the counter voltage signal lines are arranged by way of an insulation layer in many cases and the electrical connection between the counter electrodes and the counter voltage signal lines is established via small through holes formed in the insulation layer and hence, the further enhancement of the reliability of connection has been requested. This coincides with the demand for high definition in recent years.
The present invention has been made in view of such circumstances and it is an object of the present invention to provide a liquid crystal display device which can enhance the numerical aperture of pixel regions.
Further, it is another object of the present invention to provide a liquid crystal display device which can ensure the reliable connection between counter electrodes and counter voltage signal lines.
According to a first embodiment of a liquid crystal display device of the present invention, there is provided for example, on a liquid-crystal-side surface of one substrate out of respective substrates which are arranged to face each other in an opposed manner by way of liquid crystal, regions which are surrounded by a plurality of gate signal lines which are arranged in parallel and a plurality of drain signal lines which cross the gate signal lines and are arranged in parallel are defined as pixel regions. A switching element is provided which is operated in response to a scanning signal from the gate signal line, a pixel electrode to which a video signal is supplied from the drain signal line through the switching element, and a counter electrode to which a signal which constitutes the reference with respect to the video signal is supplied through a counter signal voltage signal line are formed on each pixel region. The counter electrodes are formed as layers below a laminated body consisting of a plurality of insulation layers, and the counter voltage signal lines are formed of a non-light-transmitting (opaque)conductor, are formed as layers over the laminated body consisting of the plurality of insulation layers, and form a lattice-like pattern such that the counter voltage signal lines cover the gate signal lines and the drain signal lines, and have portions thereof electrically connected to the counter electrodes via through holes formed in the laminated body consisting of the plurality of insulation layers.
According to a modification of the first embodiment of the liquid crystal display device of the present invention, for example, the electric connection between the counter voltage signal line and the counter electrode is established through another conductive layer which is formed simultaneously with a conductive layer which constitutes the pixel electrode formed between the plurality of insulation layers.
According to another modification of the first embodiment of the liquid crystal display device of the present invention, for example, the electric connection between the counter voltage signal line and the counter electrode is established through another conductive layer which is formed simultaneously with a conductive layer which constitutes the drain signal line formed between the plurality of insulation layers.
According to a further modification of the first embodiment of the liquid crystal display device of the present invention, for example, which may include any of the aforementioned modifications, the electric connection between the counter voltage signal line and the counter electrode is established at two or more positions.
According to a second embodiment of the liquid crystal display device of the present invention, there is provided on a liquid-crystal-side surface of one substrate out of respective substrates which are arranged to face each other in an opposed manner by way of liquid crystal, regions which are surrounded by a plurality of gate signal lines which are arranged in parallel and a plurality of drain signal lines which cross the gate signal lines and are arranged in parallel are defined as pixel regions. A switching element which is operated in response to a scanning signal from the gate signal line, a pixel electrode to which a video signal is supplied from the drain signal line through the switching element, and a counter electrode to which a signal which constitutes the reference with respect to the video signal is supplied through a counter voltage signal line are formed on each pixel region. The counter electrodes are formed as layers below a laminated body consisting of a plurality of insulation layers, and the pixel electrodes are constituted of a plurality of groups of electrodes which are formed between two insulation layers out of the plurality of insulation layers of the laminated body and extend along the extending direction of the drain signal lines and are arranged in parallel in the direction which crosses the extending direction. The counter voltage signal lines are formed of a non-light-transmitting (opaque) conductor, are formed as layers over the laminated body consisting of the plurality of insulation layers, and form a lattice-like pattern such that the counter voltage signal lines cover the gate signal lines and the drain signal lines, and have portions thereof electrically connected to the counter electrodes via through holes formed in the laminated body consisting of the plurality of insulation layers.
According to a modification of the second embodiment of the liquid crystal display device of the present invention, for example, when the pixel region is viewed in plan view, a distance between the counter voltage signal which is formed such that the counter voltage signal covers the drain signal line and the pixel electrode which is arranged adjacent to the counter voltage signal line is set larger than a distance between the pixel electrodes which are arranged adjacent to each other.
According to another modification of the second embodiment of the liquid crystal display device of the present invention, for example, which may include the aforementioned modifications, when the pixel region is viewed in plan view, a distance between the counter voltage signal line which is formed such that the counter voltage signal line covers the drain signal line and the pixel electrode which is arranged adjacent to the counter voltage signal line is set larger than a distance between the counter voltage signal and the counter electrode which is arranged adjacent to the counter voltage signal line.
According to a third embodiment of the liquid crystal display device of the present invention, on a liquid-crystal-side surface of one substrate out of respective substrates which are arranged to face each other in an opposed manner by way of liquid crystal, regions which are surrounded by a plurality of gate signal lines which are arranged in parallel and a plurality of drain signal lines which cross the gate signal lines and are arranged in parallel are defined as pixel regions. A switching element which is operated in response to a scanning signal from the gate signal line, a pixel electrode to which a video signal is supplied from the drain signal line through the switching element, and a counter electrode to which a signal which constitutes the reference with respect to the video signal is supplied through a counter voltage signal line are formed on each pixel region. The counter voltage signal lines are made of Al or an Al alloy which has a surface thereof anodized and each counter voltage signal line is formed as a layer below a laminated body consisting of a plurality of insulation layers. The counter electrodes are formed of a light-transmitting conductor, are formed as layers over the laminated body consisting of the plurality of insulation layers, and form a lattice-like pattern such that the counter electrodes cover the gate signal lines and the drain signal lines, and have portions thereof electrically subjected to a capacitive coupling with the counter voltage signal lines via through holes formed in the laminated body consisting of the plurality of insulation layers.
According to a fourth embodiment of the liquid crystal display device of the present invention, on a liquid-crystal-side surface of one substrate out of respective substrates which are arranged to face each other in an opposed manner by way of liquid crystal, regions which are surrounded by a plurality of gate signal lines which are arranged in parallel and a plurality of drain signal lines which cross the gate signal lines and are arranged in parallel are defined as pixel regions,
a switching element which is operated in response to a scanning signal from the gate signal line, a pixel electrode to which a video signal is supplied from the drain signal line through the switching element, and a counter electrode to which a signal which constitutes the reference with respect to the video signal is supplied through a counter voltage signal line are formed on each pixel region. The counter voltage signal lines are made of Al or an Al alloy which has a surface thereof anodized and each counter voltage signal line is formed as a layer below a laminated body consisting of a plurality of insulation layers, and each counter voltage signal line includes conductive material layers which are exposed from the counter voltage signal line at lower layers of at least portions of the counter voltage signal line. The counter electrodes are formed as layers over the laminated body consisting of the plurality of insulation layers, and form a lattice-like pattern such that the counter electrodes cover the gate signal lines and the drain signal lines, and have portions thereof electrically connected to the conductive material layers via through holes formed in the laminated body consisting of the plurality of insulation layers.
According to a modification of the fourth embodiment of the liquid crystal display device of the present invention, for example, the counter electrodes are formed of a light-transmitting conductive layer.
According to another modification of the fourth embodiment of the liquid crystal display device of the present invention, for example, which may include the aforementioned modifications thereof, the drain signal lines are formed between two insulation layers of the laminated body formed of the plurality of insulation layers, and material layers which are made of the same material as the drain signal lines are interposed between the counter electrodes and the conductive material layers.
Here, the present invention is not limited to the above-mentioned constitutions and various modifications can be made without departing from the technical concept of the present invention.